Executive task-set inertia manifests via response suppression and not vector inversion


Alternating between different tasks represents an executive function essential to daily living. In the oculomotor literature reaction times (RT) for a 'standard' stimulus-driven (SD) prosaccade (i.e., saccade to veridical target location at target onset) increase when preceded by a 'non-standard' antisaccade (i.e., saccade mirror-symmetrical to target location at target onset), whereas the converse does not elicit a switch-cost. The prosaccade switch-cost has been attributed to lingering neural activity – or task-set inertia – related to prosaccade suppression (i.e., response suppression) and decoupling stimulus-response spatial relations (i.e., vector inversion). It is, however, unclear whether response suppression and/or vector inversion contribute to this switch-cost. Here, Experiment 1 had participants alternate (i.e., AABB paradigm) between minimally delayed (MD) pro- and antisaccades. MD saccades require responses after target extinction necessitating response suppression across pro- and antisaccades – used to determine whether vector inversion contributes to a task-set inertia. In Experiment 2, participants alternated between SD pro- and MD antisaccades to determine if a task switch-cost is selectively imparted when a stimulus-driven and standard response is preceded by a non-standard response. Experiment 1 showed that RTs for MD pro- and antisaccades were not influenced by the preceding trial-type; i.e., vector inversion did not engender a switch-cost. Experiment 2 showed that RTs for SD prosaccades were increased when preceded by a MD antisaccade. Accordingly, the executive demands of response suppression engendered a task-set inertia for a subsequent stimulus-driven and standard response (i.e., SD prosaccade) – a finding supporting the view that response suppression is a hallmark feature of executive function.

Acknowledgments: Natural Sciences and Engineering Research Council (NSERC)